My kids love to have water balloon wars. I do too if I am being honest. The drag for me is that neither of my kids can tie their own balloons and tying off a bunch of balloons that will hit you is no fun. This is where the cool ThinkGeek Tie Knot Water Balloon Filler comes in.
This thing makes it easy for anyone to fill and tie off a water balloon. The thing has a push button trigger to fill the balloon. Then you twist the end of the balloon around, put the opening in the notch, and pull the balloon off.
The balloon ties itself as you removed from the filler. That is so cool and will mean my kids can handle filling their own balloons rather than asking me all the time to fill them up for them. The Tie Knot Water Balloon Filler is available right now on ThinkGeek for $9.99.